Syphilis is an infectious disease sexually transmitted with obligatory declaration and whose pathogenic agent is Treponema pallidum. It appears clinically by a succession of phases during which the Treponema can be highlighted by direct or indirect methods. The existence of quiet clinical phases during which the diagnosis is not currently possible that by test serologic one of the major difficulties of the tracking of syphilis constitutes. Before accusing a psychiatric cause, we carry out a research of the neurosyphilis systematically. Indeed, this can associate a neurological syndrome being able to lead the complete physical forfeiture or a driving psychiatric syndrome in a true irrational state. Our work concerned 8251 serums and 134 LCR (spinal puncture) coming from patients addressed to the psychiatric hospital of Razi from January 1996 to December 2003 for serology of syphilis and neurosyphilis. Half of the patients had an age ranging between 40 and 60 years, 70% were unmarried and 80% were without job. Our syphilitic serology comprised each time two reactions: agglutination (VDRL coal) and specific passive haemagglutination (TPHA). The results showed a prevalence of the disease syphilitic serum and neurological at the man (65–70%) what is in conformity with the literature. The prevalence of serum syphilis is higher in the age breaked ranging between 20 and 45 years; it should be counted a few years before the neurosyphilis is not declared. 60–80% of our patients are unmarried (reflexion of a great freedom of manners) and without job; a better social integration could make regress the disease. We noticed that the prevalence decreased as for syphilitic serology (it passed from 7.6% in the 5 years of 1986–1990 and 4.7% of 1991–1995 than finally to 2.9% currently). On the contrary, the prevalence of the neurosyphilis appreciably increased passing from 1.6 to 3.47% in 10 years. The efforts provided in regards national fight against the MST thus seem to give results concluding, although cases of neurosyphilis continue to be reported.